This invention relates to the field of motor speed changers and in particular the field of motor speed changers including jackshafts for changing the output speed of an electric motor.
Electric motors are used as prime movers in a great variety of applications, and many of those applications require a driving speed which is not readily available from standard electric motors. The output speed of electric motors is not normally variable so that in many instances a jackshaft speed changer arrangement must be provided to either increase or decrease the motor speed to a desired output speed. Many arrangements to accomplish this have been provided in the prior art. For instance in one arrangement, disclosed in U.S. Pat. No. 3,813,956, a speed changer is provided which is secured to the face of an electric motor by means of special fasteners and wherein a number of gears are used to provide an output speed of a jackshaft which is different from that provided by the output shaft of the motor. Several problems are inherent in this arrangement. For instance, special fasteners must be provided for securing the speed changer to the electric motor and the electric motor must be provided with special threaded apertures for receiving the fasteners. Additionally, the use of gears and timing belts is expensive and, furthermore, makes it difficult and time consuming to change the output speed of the speed changer.
In other prior art structures, mounting platforms have been provided for mounting a speed changer wherein the platform did not mount directly on the electric motor. Therefore, both the motor and the speed changer mounting platform had to be mounted separately on a base. In many applications, space is limited and this arrangement is unsatisfactory. Additionally, the alignment between the output shaft of the motor and the jackshaft in these arrangements becomes difficult to achieve because of the independent mounting of the motor and the speed changer.
In other prior art arrangements complicated bracket assemblies have been provided in order to mount a jackshaft on an electric motor. The expense of the numerous parts involved in these assemblies as well as the expense of assembling those parts is a severe disadvantage in those arrangements.
An additional problem which has been encountered in the prior art arrangements is that motor designs vary from one manufacturer to another. Therefore, in the prior art arrangements wherein the jackshaft is mounted directly on the housing of the electric motor a speed change could only be used with one motor design from only one manufacturer. This required stocking of additional motor speed changers for the different motor designs with the attendant expense inherent therein.
It is therefore desired to provide a universal unitary speed changer for mounting directly on an electric motor and which can be mounted on a variety of motors.
It is furthermore desired to provide a speed changer for mounting on an electric motor which is easy to mount and which can be mounted in a variety of positions.
It is also desired to provide a speed changer for an electric motor which is inexpensive and wherein the output speed can be changed easily.